After the blood circulation stops in the body of the deceased, blood and other body fluids move to the lower parts (under the influence of gravity) according to the laws of physics . In this case, the blood begins to flow from the arterial vessels into the venous and overflows them. It should be noted that the vascular walls are characterized by increased permeability. In this regard, the blood begins to leak out of the vessels and accumulate in the tissues. As a result, early cadaveric changes begin. Leaked blood gives the skin the appropriate color. As a rule, cadaverous spots are dirty-lilac with predominance of different shades. These shades depend on the cause of death and other factors.
So, for example, if death came from poisoning with carbon monoxide, then the cadaveric spots are bright red. This is due to the fact that hemoglobin passes into carboxyhemoglobin. If there was poisoning with cyanide compounds, the cadaveric stains will have a peculiar cherry tint. The corpses that were in the cold, they will be bright pink. This is due to the fact that hemoglobin is oxidized by air oxygen, which penetrates through the microcracks of the skin. In turn, microcracks are formed due to the freezing of liquids in the body.
If there are spots on the body from behind, then this indicates that the corpse was on its back. If the deceased was located on the stomach, then, respectively, they appear on the front surface. If there was a hanging and the corpse was not removed for a long time from the loop, then the cadaveric spots are located mainly on the feet, legs, forearms.
Within twelve hours after death, the hypostasis stage continues. The liquid component of blood is located in the vessels. Blood presses away from the vessels when pressed, and when the pressure stops, fills them again. This contributes to the disappearance of cadaveric spots and their movement when the body moves to the lower parts.
After twelve hours, the stage of diffusion (stasis) begins. It lasts up to twenty-four hours. In this case, the cadaveric spots begin to turn pale, but do not completely disappear. This is due to the fact that, stretching the vascular wall, the liquid part of the blood begins to penetrate into the tissue. At the same time, hemolysis of red blood cells begins. At this stage, when the position of the body is changed, the movement of cadaveric spots does not occur, but their intensity decreases to some extent.
On the second day after death, the stage of imbibition begins. At this stage there is a good fixation of cadaveric spots, they do not move, do not turn pale when pressed. This is due to the fact that soft tissues are impregnated with blood.
The extent to which cadaveric spots are expressed depends on the nature of the pathology, the cause of death, and the mechanism of dying itself. In the case of death with prolonged agony, from acute blood loss, there is a weak expression. With rapid death, for example, from electric trauma, mechanical asphyxiation and other things, the degree of expression is much higher.
It must be said that the presence of cadaver spots is the earliest sign of the onset of death. It is they who show the position of the body directly upon dying and the likely changes in the situation after death. For some particular features of cadaveric spots, you can determine the time when a person died.
After the death, there is a relaxation of the muscles. They become supple and soft. After two or four hours, signs of rigor mortis begin to appear. All muscles acquire firmness, become dense, somewhat contracted, fixing the posture (position) of the body. To change the pose of the deceased, it takes a considerable effort.